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UNIVERSITY   OF   CALIFORNIA  Agricultural  Experiment  Station 

College  of  agriculture  e,  w.  hilgard,  director 

BERKELEY,  CALIFORNIA 


CIRCULAR  No.  8. 


Laboratory  Method  for  Ordinary  Chemical  Examination  of 

Waters  for  Irrigation  and  Domestic  Purposes. 


Note.— The  methods  here  given  are  intended  merely  for  tests  of  waters  for  ordinary 
purposes,  such  as  irrigation  and  domestic  use,  and  are  nowise  intended  to  supersede  the 
more  elaborate  and  accurate  methods  given  in  books  on  water  analysis,  when  such  are 
necessary. 

Preparation  of  Standard  Solutions.     (See  Sutton's  Volumetric  Analysis, 
8th  edition.) 

A.  Standard  Silver  Nitrate.  The  strength  of  this  solution  should 
accord  with  directions  given  on  p.  151,  8th  ed.,  Sutton. 

B.  Standard  Ammonic  Thiocyanate.  The  strength  of  this  solution 
should  be  such  that  it  will  balance  the  solution  of  silver  nitrate  A. 

C.  Standard  Sulfuric  Acid.  This  solution  must  contain  0.00098 
gram  S03  per  cc,  i.  e.,  it  should  exactly  neutralize  solution  D. 

D.  Standard  Sodium  Carbonate  Solution.  Each  cc.  to  contain 
0.00106  gram  sodium  carbonate  (see  pp.  47  and  49,  Sutton). 

Determination  of  Total  Residue. 

1.  Evaporate  100  cc.  to  dryness  in  weighed  platinum  dish  on  water 
bath.  Dry  at  110°  C.  for  one  hour;  cool  and  weigh,  then  heat  and  weigh 
again,  or  until  constant.     Result  equals  the  total  solids. 

2.  Gently  ignite  (below  redness)  the  residue;  cool  and  weigh.  The 
loss  in  weight  generally  can  be  taken  as  "organic  matter  and  chemically 
combined  water." 

Exceptions — 

(a)  If  the  water  contains  nitrates  in  appreciable  quantity,  then 
the  loss  will  include  some  nitric  acid. 

(b)  If  the  water  contains  much  magnesium  carbonate,  some  of 
the  loss  in  weight  would  be  due  to  the  carbonic  acid  belonging'  to 
the  magnesium. 

(c)  If  the  water  contains  much  CaCl2  or  MgCL,,  then  the  loss  in 
weight  can  not  be  taken  as  organic  matter  and  chemically  com- 
bined water  only. 

Note  any  change  of  color  during  the  ignition.  A  blackening  of 
the  residue  would  indicate  the  presence  of  organic  matter;    in  some 


—  2  — 

cases  iron  oxid.  If  nitrates  are  present  there  will  be  evolved  character- 
istic red  fumes,  and  blackening  may  not  occur  even  in  presence  of 
organic  matter. 

Separation  of  the  Soluble  and  Insoluble  Salts. 

3.  Treat  the  residue  in  the  dish,  after  ignition,  with  a  small  quantity 
of  60  per  cent  alcohol  to  exclude  gypsum,  filter  through  a  small  paper 
into  a  50  cc.  graduate.  The  nitrate  and  washings  should  not  exceed 
20  cc.  Make  the  solution  up  to  40  cc.  or  50  cc.  This  solution  (A)  con- 
tains salts  of  sodium  and  potassium,  and  the  following  salts  if  present 
in  the  original  water — calcium  and  magnesium  chlorids,  magnesium 
sulfate,  etc. 

4.  Burn  the  filter  from  previous  nitration,  containing  the  insoluble 
part  of  the  total  residue,  on  side  of  dish,  at  as  low  a  temperature  as  will 
suffice  for  complete  incineration.  Moisten  with  water,  recarbonate  with 
carbonic  acid  gas;  dry,  cool,  and  weigh.  The  loss  in  weight  represents 
the  soluble  part  after  evaporation,  contained  in  solution  A. 

5.  Residue  in  dish  consists  of  the  insoluble  part  after  evaporation, 
viz.:  calcium  and  magnesium  carbonates  and  phosphates,  calcium  sul- 
fate, iron  oxid  (originally  present  as  carbonate  in  most  cases),  alumina, 
silica,  etc.  Treat  the  residue  with  small  quantity  of  HC1  (desk  acid). 
Note  amount  of  effervescence  (indicative  of  carbonic  acid).  Evaporate 
to  dryness  on  sand  bath,  thus  rendering  silica  insoluble.  Treat  the  con- 
tents of  dish  with  HC1  and  water;  evaporate  to  dryness;  digest;  treat 
with  dilute  HC1;  filter  off  the  silica  (solution  B),  burn  filter,. weigh. 
Loss  in  weight  consists  of  the  insoluble  part  less  silica;  the  residue  in 
dish  is  silica. 

A  convenient  form  of  recording  the  results  of  the  above  work  as  it 
progresses  may  be  stated  as  follows: 

Amount  of  water  taken. cc. 

Dish  and  Residue  at  100-110°  C _. 

Dish,  less  organic  matter  and  chemically  combined  water 

Dish,  less  soluble  part 

Dish,  less  insoluble  part,  including  silica _ 

Dish 

Residue  (total) .._ ,. 

Organic  matter  and  chemically  combined  water 

Soluble  part _- 

Insoluble  part,  less  silica. 

Silica. ...^ 

Analysis  of  the  Soluble  Part,  Solution  A. 

1.  Take  10  cc,  determine  the  alkalinity  with  N/50th  sulfuric  acid, 
methyl  orange  indicator;  calculate  to  sodium  carbonate.  Each  cc.  acid 
equals  0.00106  gram  sodium  carbonate. 

2.  Take  another  10  cc.  and  determine  the  chlorin,  after  evaporating 
off  the  alcohol,  with  N/lOth  silver  nitrate  (1  cc.  of  which  is  equivalent 
to  0.0058  gram  sodium  chlorid). 


/  «* 


—  3  — 

Make  qualitative  tests  for  Ca,  Mg,  S03,  etc.  If  no  calcium  or  magne- 
sium is  present,  then  all  the  chlorin  may  be  calculated  as  sodium 
chlorid,  and  the  sum  of  this  and  the  sodium  carbonate  taken  from  the 
total  soluble  salts  leaves  chiefly  sodium  and  potassium  sulfate,  with 
possibly  borates.  Lithium  is  to  be  tested  for  in  a  separate  evaporated 
portion  of  water  by  the  spectroscope ;  also  for  boracic  acid. 

Analysis  of  the  Insoluble  Part,  Solution  B. 

Make  up  the  solution  in  hydrochloric  acid  to  50  cc,  or  any  convenient 
amount.  In  small  portions  of  this  test  qualitatively  for  calcium,  mag- 
nesium, alumina,  iron,  and  the  acids — sulfuric  and  phosphoric,  etc.  If 
necessary,  determine  calcium  and  sulfuric  acid  in  aliquot  portions.  All 
the  sulfuric  acid  should  be  calculated  as  calcium  sulfate,  or  gypsum. 
The  remainder  of  calcium  is  combined  with  carbonic  acid  to  form  cal- 
cium carbonate. 

If  appreciable  amounts  of  iron  and  alumina  are  present  they  should 
be  determined,  and  the  iron  is  usually  calculated  to  ferrous  carbonate; 
otherwise  they  can  be  included  in  the  expression  "Calcium  and  magne- 
sium carbonates,  etc.,"  in  the  final  report,  as  below.  (Silica  is  deter- 
mined, as  already  stated,  at  the  last  weighing  of  the  process  of  obtaining 
the  soluble  and  insoluble  salts.)  Strontium  and  barium  are  to  be  tested 
for  by  the  spectroscope, 

CALCULATION    OF    RESULTS. 

Divide  milligrams  per  liter  by  17.12;  the  result  gives  grains  per  U.  S. 
gallon. 

Chlorin:  When  100  cc.  of  water  is  evaporated  and  the  soluble  part 
made  up  to  40  cc.,then  if  10  cc.  of  the  solution  (equivalent  to  25  cc.  of 
the  original  water)  are  taken  for  titration: — 

Grains  per  Gallon.  Parts  per  10,000. 

NaCl.  NaCl. 

1.0     cc.  T*   standard  AgN03 13.64  or  2.33 

0.5        "              "               "        6.82  "  1.17 

0.1        "              "               "        1.364  "  .233 

0.05      "              "               "        -       .682  "  .117 

0.01      "              "               " -- .136  "  .023 

Sodium  Carbonate:  When  100  cc.  are  evaporated  and  the  soluble 
part  made  up  to  40  cc.  and  10  cc.  taken  for  titration  with  -\  acid: — 

Grains  per  Gallon.  Parts  per  10,000. 

Na2C03.  Na2C03. 

0.5cc./Dacid 1.22  0~.21 

1.0        "        "     2.44  0.42 

1.5        "        '      .--.       3.66  0.63 

2.0        "        "     ---.       4.88  0.84 

2.5        "        "     6.10  1.05 

3.0        "        "     7.32  1.26 

The  student  should  also  consult  tables  on  pp.  531-532,  Sutton's  Volu- 
metric Analysis.  " 


—  4  — 

FORM    FOR    REPORTING    RESULTS   OF  ORDINARY    ANALYSIS   OF   WATER. 


Source  .. 
Locality 
Sender  . . 


Soluble  Portion.  per  Gallon.  per  10,000. 


Potassium  Sulfate 

Sodium  Sulfate  (glauber  salt),  etc 

Sodium  Chlorid  (common  salt) 

Sodium  Carbonate  (sal  soda) 

Calcium Magnesium 

Insoluble  Portion. 
Calcium  and  Magnesium  Carbonates,  etc. 

Calcium  Sulfate  (gjrpsum) 

Silica 

Organic  matter 

and  chemically  combined  water 

Total 


NITROGEN   AS   NITRATES    (SPRENGEL    METHOD). 

Solutions  Required: — 

Phenol-Sulfonic  Acid:  37  cc.  of  strong  sulfuric  acid  are  added  to 
3  cc.  of  water  and  6  grams  of  pure  phenol;  heat  on  water  bath  for  from 
3  to  6  hours. 

Standard  Potassium  Nitrate:  0.722  gram  of  KNOs,  previously  heated 
to  a  temperature  just  sufficient  to  fuse  it,  is  dissolved  in  H20  and  the 
solution  made  up  to  1000  cc.  1  cc.  of  this  solution  will  contain  0.0001 
gram  of  nitrogen. 

Analytical  Process: — 

A  measured  volume  (25  cc.)  of  the  water  is  evaporated  just  to  dry- 
ness in  a  porcelain  basin.  1  cc.  of  phenol-sulfonic  acid  is  added  and 
thoroughly  mixed  with  the  residue  by  means  of  a  glass  rod.  1  cc.  of 
water  is  added,  then  three  drops  of  strong  H2S04,  and  the  dish  gently 
warmed  on  the  water  bath. 

The  liquid  is  then  diluted  with  25  cc.  of  water,  ammonia  added  in 
excess,  and  the  solution  made  up  to  50  cc. 

The  nitrate  converts  the  phenol-sulfonic  acid  into  picric  acid,  which 
by  the  action  of  the  ammonia  forms  ammonium  picrate;  this  imparts 
to  the  solution  a  yellow  color,  the  intensity  of  which  is  proportional  to 
the  amount  present. 

Since  ammonium  picrate  solution  keeps  well  in  the  dark,  a  good  plan 
is  to  make  a  solution,  equivalent  to,  say,  10  milligrams  of  N.  as  nitrate 
per  liter,  to  which  the  color  obtained  from  the  water  may  be  directly 
compared. 

(The  ammonium  picrate  on  the  shelf  is  so  made  that  1  cc.  equals 
0.000025  gram  N.) 


